1. Field of the Invention
The present invention relates generally to truck apparatus for skate and skateboard devices, and more particularly to a truck assembly having readily adjustable kingpin angle and torque resistive features.
2. Description of the Prior Art
Although the prior art is replete with configurations of skate and skateboard truck mechanisms, all previous designs may generally be categorized into two general classes; i.e., the class in which the truck axle is constrained more or less rigidly to rotate about a fixed kingpin axis with rotation about the kingpin axis being resisted by some type of resilient member that is typically placed in both shear and compression simultaneously, and the class of configurations in which the primary loading to the truck is carried by a heavily bushed stud bolt and the truck turn radius is determined by an arm that extends from the truck axle to pivotally intersect either the bottom of the skate board or a truck-mounting plate. Examples of the former type of truck are illustrated in the following U.S. Pat. Nos: Balstad, 2,466,070 and 2,595,751; Crone, 2,763,490; Crone 2,920,899; Ware, 3,087,739; Butler, 3,442,523, Balstad, 3,870,324; Pinchock 4,047,725; and Kimmell, 4,071,256; while examples of the latter are disclosed in the U.S. patents to Machatsch, U.S. Pat. No. 3,774,924; Holladay et al, U.S. Pat. No. 4,047,727; Oldendorf, U.S. Pat. No. 4,060,253; and Widolf, U.S. Pat. No. 4,103,917.
Basically, the turning of a skate or skateboard is accomplished by a shifting of the rider's weight to an off-center position on the supporting platform so as to cause a torquing movement about the various supports. As a result, the supporting bushings are compressed or torqued such that the resolution of forces about the axes of the various support members causes the truck axles to rotate about more or less determinable axes angularly intersecting the supporting platform and as a result causing each truck wheel set to turn relative to the longitudinal axis of the supporting surface. However, in most cases, the turning action is nonuniform and nonreproducible because different variations of side loading cause different angular orientations of the truck axles, and conversely, different reductions in side loading cause different restoring forces to be applied to the truck axles.
One disadvantage of such prior art structures is that since turns are effected by compressing or otherwise stressing a block of resilient material, the restoring force is more or less proportional to the angle of turn, and as a consequence where the rider attempts to maintain a sharp turn he must continuously exert a substantial force against what is usually a strong restoring force. As a result, any inadvertent shift in weight allows the restoring force to abruptly change the turning angle of the truck, in many cases to the extent that it causes the rider to at least momentarily lose his balance and control. It would be much more desirable if the restoring force was selectable and constant for all angles of turn.
Another disadvantage of the prior art is that with the exception of the angle pad accessory disclosed in the above-mentioned Oldendorf patent, none of the prior art truck assemblies provide means allowing a simple selective adjustment of the kingpin axis angle and thus do not allow a rider to select the turning characteristics most suited to his skill.
Still another disadvantage of the prior art truck configuration is that very high shear and compression loads are placed upon the resilient elements with the result that their useful life is quite limited.